In this inclusive investigation into the structure of the ear and temporal bone, we are concerned with normal and pathological anatomy, both developmental and adult, in relation to the problems which arise in the practice of otology. Because the auditory ossicles and the otic capsule retain, to a striking degree, the histological architecture and the physical dimensions and relationships which were there prenatally, study of the embryological and fetal stages consistently precedes, and is explanatory of, the condition in the fully developed ear. Completed phases of the investigation are periodically published in clinical journals, are presented as papers on the programs of the American Otological Society, the Triological Society, the Academy of Ophthalmology and Otolaryngology, and the American Association of Anatomists. Finally, all material will appear in a monographic treatise.